You are not being unreasonable, and unfortunately the only way it's going to resolve itself is by your DP having the courage to put a stop to it, which may take time. I don't know what it is about ex's but they seem to manage to be an ex, and still be extremely manipulative/controlling at the same time, and for some bizzare reason, DP's seem happy to pussy foot around them until things reach crisis point.
She's being incredibly rude, and it's almost as if she's doing it deliberately to see how far she can push it. Normal people wouldn't dream of doing what's she's doing.
That aside, you have to decide how much more you're prepared to take. If he won't put a stop to it, you only have 2 choices. Put up with it and hope it resolves in time, or leave. If you decide you can't live like this any more, tell your DP that, and tell him he has a choice. Either he puts a stop to it, or he lets it continue, in which case you're out of there.
By the way, from experience, he's probably scared to take a stand in case he looses his kids. What he doesn't realise is that by letting his ex walk all over him, and you, they will see him as spineless and whilst they will still love him, they won't respect him, and in time, they'll walk all over him too. Also she's not struggling. She's using him, and you, and he's letting her.